This invention relates to bioremediation of wastewater, and more particularly to a method and apparatus for treating wastewater flowing thorough a sewer with a solid or dry bioremediation preparation.
Public wastewater collection and treatment systems typically consist of networks of underground pipes and conduits, wet wells, and pumping/lift stations that carry wastewater (e.g., waste from sanitary sewer systems) to a wastewater treatment plant. After entering the treatment plant, the wastewater is commonly subjected to primary, secondary and tertiary treatment processes to remove solid matter and other substances from the wastewater.
Public wastewater collection and treatment systems can be subject to a number of expensive and noxious problems. Such problems typically result from or consist of a) build-up of congealed grease or organic matter within pipes or other conduits, b) the formation of grease layers known as xe2x80x9cmatsxe2x80x9d on the surfaces of wastewater that pools within wet wells or lift stations; c) anaerobic septic conditions, d) bad odors due to the production of hydrogen sulfide and/or other gasses, e) acidic corrosion due to hydrogen sulfide gas, and f) disease-causing bacteria. If left unchecked, these conditions can cause expensive pipe and equipment damage, pipe blockages, backed up sewer lines, raw sewage spills and health problems in humans and/or animals within the community.
Various methods of coping with these problems have been tried in the past. The following are examples of such prior methods of coping with these problems:
i. Mechanical Dislodgement or Purging of Obstructions
Various mechanical processes have been used to dislodge and remove built-up coatings of congealed grease, sludge deposits, oil and soap in sewer lines and lift stations. The mechanical processes include the use of water pressure jets, vacuum trucks, xe2x80x9croto-rootingxe2x80x9d and a process known as xe2x80x9cpiggingxe2x80x9d or xe2x80x9cballingxe2x80x9d where a ball is forced and/or pulled through the wastewater line. These mechanical processes are high in labor, equipment and removal costs. The dislodged pieces of material have to be collected and taken to a disposal site.
ii. Chemical Treatments
Solvent and enzyme products can be used to liquefy and disperse the grease. The required products are costly. This method often times does not reduce the oil and grease in the collection system, but merely passes the problem downstream as the oil and grease may tend to re-solidify, thereby re-coagulating in pipes and pump stations or re-forming in the wastewater treatment plant.
Chemicals such as calcium nitrate, sodium nitrate, chlorine, hydrogen peroxide, caustic soda, lime and iron salts can be used in the short-run to control the bacteria and other conditions responsible for the generation of odorous and corrosive hydrogen sulfide gas. The use of chemicals in sufficient quantities in the long-run is not only very expensive, but there are operational and safety problems. Chemicals can kill the beneficial microorganisms which are the heart of the waste treatment plant, and create ecological problems beyond the plant. However, the currently available chemical storage and delivery apparatus useable for this purpose typically require an above-ground storage structure as well as a source of electrical power, which may be unavailable at many locations in a municipal wastewater treatment system. Moreover, chlorine is highly toxic and can form hazardous compounds such as trihalomethanes (THMs) which are known carcinogens. Hydrogen peroxide is an oxidizing agent less harmful than chlorine, but it has safety and handling issues. The same applied to caustic soda and iron salts, which are corrosive in their own right and can damage plant and equipment like the hydrogen sulfide gas they are supposed to mitigate.
iii. Microbiological Treatments
Another approach involves the use of naturally occurring beneficial microorganisms and catalysts or biostimulation additives (e.g. mixtures or complexes of vitamins, amino acids, enzymes, minerals, organic acids and nutrients) that can stimulate the growth of aerobic and facultative microorganisms indigenous to the system or those aerobic and facultative organisms that are being added to the wastewater stream. These additions of catalysts and microorganisms are meant to establish a more balanced flora or indigenous microbial growth in the system, to remove slime layers populated by anaerobic microorganisms and to remove decomposing organic waste material both of which cause or are caused by septic conditions from which hydrogen sulfide and other odorous compounds are generated. The use of bioremediation and/or bioaugmentation products can also deter the formation of grease and organic material build-ups before such build-ups can cause obstruction of the wastewater collection system. Results achieved by removing anaerobic slime layers, organic material and congealed grease, oils and soap build-up can be a reduction or elimination of both dissolved and gas phase hydrogen sulfide and other noxious odors, reduction or elimination of build-up of organic deposits resulting in faster wastewater flow through the piping, reduction or elimination of acidic corrosion of pipes, manholes, wet wells and equipment and cleaner wastewater with a higher level of dissolved oxygen. The results are a dramatic drop in noxious odors, reduced or eliminated buildup of organic deposits, cleaner wastewater with a higher level of dissolved oxygen, faster flow through pipes, and control of costly acidic corrosion due to hydrogen sulfide.
This approach, known as bioremediation, requires the introduction of microorganisms and bio-stimulators at a controlled rate into the waste water collection system. This has previously been done by spraying, pumping or otherwise delivering a liquid microbial solution into the collection system at various points such as wet wells and pumping stations. Liquid solutions, however, have a limited shelf life and require above ground storage as well as the availability of a power source, such as an electric outlet in the immediate vicinity of the solution-dispensing location. Additionally, not all microorganisms that are desirable in bioremediation can be prepared in a stable, liquid solution.
Dry bioremedial powders have been developed to greatly increase shelf life, and the variety of beneficial microorganisms that may be included in the treatment, however the use of these dry bioremedial powders in the field has been limited due to the lack of a dispensing apparatus capable of withstanding the high-humidity, corrosive atmosphere of the waste water collection system, and capable of keeping the powder dry to prevent caking and to assure reliable operation for extended periods of time without an external power source.
iv. Methods and Apparatus Previously Used for Delivering Chemical and/or Microbiological Treatments to Wastewater
In addition to manual distribution, various other methods and apparatus have heretofore been used for delivering liquid and dry biological or chemical treatments to wastewater at various locations in the wastewater collection/treatment system.
A. Peristaltic Pumps and Gravity Drip Systems for Adding Liquid Biological and Chemical Treatments
Liquid biological and enzyme products (e.g., Neozyme(trademark) and Microbac(trademark)) useable for controlling grease build-up, as well as certain liquid bio-stimulants (e.g., Bioprime(trademark), Neozyme(trademark) and BioCatalytics(trademark)) that purportedly are useable for odor control, can be delivered into flowing wastewater streams at wet wells, lift stations or pumping stations. Peristaltic pumps typically require a separate source of electrical power and liquid preparations typically require above-ground storage, and thus are not suitable for use within a manhole at a remote site away from all electrical power sources. Gravity drip systems can be installed within man holes located at remote sites away from all electrical power sources but such locations typically do not include the above-ground storage facility required to house the liquid treatment preparation being fed to the gravity drip system. Moreover, both peristaltic pumps and gravity drip systems are useable only with liquid biological or chemical treatments and can not be used to deliver solid (e.g., powdered or pelletized) biological or chemical treatments. Also, drip systems are subject to clogging and may not accurately deliver controlled dosages of the liquid.
B. Permeable or Dissolvable Bags for Delivering Dry Biological Treatments
Permeable (e.g., cheesecloth or cotton material) or dissolvable bags or xe2x80x9csocksxe2x80x9d have been filled with dry biological treatment materials and suspended in areas of the wastewater collection system (e.g., wet wells, manholes) such that the dry biological treatment material is delivered into the wastewater stream. An example of one such permeable bag or sock is described in U.S. Pat. No. 4,810,385 (Hater et al.) Permeable bags typically last only 2-3 weeks. Dissolvable bags can be constructed to last longer than 2-3 weeks. However, neither the permeable nor dissolvable bags have been routinely used in high-flow areas of the wastewater stream (e.g., at manholes located on lateral or trunk lines of the system) because the high flow rate of the waste water causes the dry treatment material to wash out too quickly, the rate of dissolution/dispersion of the treatment material is difficult to control and the use of these permeable or dissolvable bags may be subject to human error (i.e., forgetting to replace the bag).
C. Compressed Masses of Dry Biological Treatment Materials
Dry biological treatment materials have been prepared in dissolvable masses such as compressed bars or pucks that can be submersed in wet wells or sewer pipes to provide slow release of the biological treatment material. These dissolvable masses are not typically used in high-flow regions of the wastewater system, as they would be carried down the sewer pipe by the rapidly flowing wastewater.
The present invention generally comprises a method and feeder apparatus for feeding predetermined amounts of a dry bioremedial or microbial treatment preparation into a stream of wastewater. The feeder apparatus may be self-powered and sufficiently moisture resistant to be positionable within a manhole or other location that is devoid of electrical power, such that it will feed controlled amounts of the dry microbial treatment preparation into wastewater that is flowing within the manhole. The dry microbial treatment preparation is in a suitable dry form, such as a powder, pellets, paper impregnated with dry microbial matter, dissolvable or frangible packets or bags containing the dry microbial treatment preparation or any other type of dry dosage delivery format. The feeder apparatus may incorporate any suitable type of delivery apparatus for feeding the dry microbial treatment preparation into the wastewater stream. In applications where the dry microbial treatment preparation is powdered or pelletized, the feeder apparatus may incorporate an auger or screw-type feeder that is rotationally driven, continuously or periodically, to deliver the desired doses of the powder or pelletized microbial treatment preparation. Alternatively, in applications where the dry microbial treatment preparation is in the form of a roll of paper whereon or wherein the microbial material is contained (or a roll of interconnected, individual dissolvable or frangible packets containing the dry microbial treatment preparation) the feeder apparatus may comprise a reel and cutter system that operates to continuously or periodically unroll, cut off and release a desired length of a paper, or a desired number of the interconnected packets, into the wastewater stream. Because the feeder apparatus is self-powered, it may be positioned within man-holes or at other locations that are devoid of electrical power sources. This allows the feeder apparatus to be located upstream of a wet well, pumping station, siphon line or other location where odor or grease build up has become a problem. In this manner, the present invention makes practical the widespread use of solid-formulation bioremediation at low cost by providing a self-contained feeder system that delivers dry microbial treatment preparations directly into the waste stream at any location irrespective of the non-availability at that location of electrical power or above ground storage.
Further in accordance with the present invention, there is provided a feeder device of the foregoing character that is capable of automatic, hands-off operation. It dispenses precisely metered amounts of material on a programmable timed basis. The feed times can be programmed for the number of times per day it will feedxe2x80x94the number of events, and the length of time it will feed during the event. Timing is preset for specific flow rates, ambient temperatures, and pollutant levels. The device is preferably sufficiently air and water-tight to be useable in humid, corrosive or hostile environments.
Still further in accordance with the present invention, the feeder apparatus may comprise a housing for storing a solid microbial treatment preparation; an outlet through which the solid microbial treatment preparation may pass out of the housing; a dispensing apparatus arranged to convey the solid microbial treatment preparation from a location the housing and outwardly through the outlet; a motor arranged to drive the dispensing apparatus; a controller programmed to operate the motor for predetermined lengths of time at predetermined intervals and a battery arranged to power the motor and controller. The feeder may also comprise a support apparatus for hanging the feeder from a manhole rim or cover or otherwise mounting the feeder within a manhole.
Further in accordance with the invention, the feeder my be substantially sealed to prevent moisture from causing caking (e.g., clumping) of the solid particulate substance within the feeder. This apparatus may be installed in collection systems at problem lift stations and wet wells, or it may be positioned within a manhole or other site that is a) up-stream of a wet well or lift station, b) devoid of any source of electrical power, and c) in a relatively high-flow or low-flow region of the wastewater collection system. In this manner, the apparatus may be located to efficiently pre-treat the flowing wastewater to prevent the occurrence of odors (e.g., hydrogen sulfide generation) or build-up of matter such as sludge, fats, oil and grease at problem locations such as sewer lines, lift stations or pumping stations. The number and location of the units installed is determined based on collection system layout, pollutant loading data, and historical operating experience. Other pertinent factors such as flow rates, volume/velocity/type of waste, density of high-emission locations (e.g., restaurants that emit grease or industrial plants that emit organic waste) and the nature of local pre-treatment regulations may also be considered and the feeder apparatus may be specifically programed and positioned in light of all such factors.
Still further in accordance with the invention, the dispensing apparatus of the feeder may comprise an auger feed system for conveying the solid particulate substance out of the outlet at a controlled flowrate and/or at controlled intervals.
Still further in accordance with the invention, this apparatus of this invention may be fully self-contained and powered by a 12 VDC battery such that it requires no outside power. Remote control and monitoring may optionally be provided. Also, an optional manhole bracket assembly and suspension tether (e.g., a chain) allow for ease of installation in most manholes. The bracket may be made a corrosion resistant material (e.g., aluminum) and the chain may be made of steel and polycoated to resist corrosion.
The method of the present invention generally comprises the placement of an apparatus of the above-summarized type within a manhole or at some other area of a wastewater treatment system and using the apparatus to deliver a dry biological or chemical treatment material at a controlled flow rate, or in known quantities at controlled intervals. Because the apparatus is self-powered and self-contained it may be placed at a remote location in a fast-flowing wastewater feed line to effect pretreatment of the flowing wastewater before it reaches a wet well, lift station, pumping station or other location at which odor, sludge build-up or grease build-up is a problem.
Further in accordance with the method of the present invention, an apparatus for delivering a dry microbial wastewater treatment preparation may be located at a sufficient distance upstream of the location at which an odor problem or build-up of sludge or grease is detected to substantially prevent the occurrence of such odor problems or build-up of matter. By adding the dry microbial preparation upstream of the actual location at which the odor or matter build-up is perceived, the present invention can deliver a microbiological treatment that will establish an aerobic/facultative digestion cycle in the wastewater lines and lift stations, eliminating grease and organic build-up and deterring the anaerobic environment necessary for growth of sulfur-related bacteria and the resultant generation of H2S and other odor producing compounds. The feeder apparatus may be programmed to deliver a consistent microbial dose that is sized to the volume of wastewater flow through the line or system, the overall length of the wastewater system and the magnitude of the pollutant load. The feeder apparatus used to deliver the dry microbial preparation may be specifically programmed to vary the amount of the microbial treatment that is being delivered to correspond to variations in the flow rate or volume of the wastewater passing through the conduit and/or variations in the pollutant load contained within the wastewater. Healthy microbial colonies are thus established in the piping and wet wells, removing old deposits of sludge and grease and preventing new organic deposits from forming. Functionally, the use of the present invention effectively turns the collection conduits that lead to the wastewater treatment plant into a xe2x80x9cpre-treatment plant digesterxe2x80x9d so as to eliminate odor, improve water quality and lower the solids and pollutant content of the wastewater that reaches the treatment plant. The use of the present invention in accordance with this method results in reductions in fats, oils and grease (FOG), biological oxygen demand (BOD), chemical oxygen demand (COD), ammonia (NH3), nitrogen or nitrogenous compounds (N), suspended solids (VSS) and/or total solids (TS). When the feeder apparatus is self-powered and self-contained, in accordance with this invention, it may be placed at a remote location in a wastewater line that is devoid of electrical power, to pre-treat the wastewater before it reaches the location at which odor, sludge, or build-up of grease and/or other matter is a problem.